Consumer markets continue to request portable electronic devices that are smaller and provide more advanced features.
Examples of such devices include compact disc players, two-way radios, cellular telephones, and computer devices to name but a few. As such devices become smaller, the demand for smaller portable energy sources to power these devices increases.
Electronic circuits operating at lower voltages have helped reduce energy consumption of such devices and, accordingly, have helped reduce the sizes of the portable energy sources required to operate the devices over reasonable periods of time. Some circuits, such as amplifier circuits, however, continue to operate most efficiently at higher voltages.
Despite low voltage advancements, a portable energy source may still be too bulky, too heavy, or may not last long enough for many high power applications. For one, a portable energy source, such as a battery or battery pack, must often deal with short term surges in currents drawn by a device. The battery must be robust enough to provide a peak current that may be substantially higher than an average current of the device. Therefore, the battery may often have a larger size to meet the power requirements of the device even though a smaller battery would be sufficient for the energy requirements.
To help alleviate these problems, a device may be powered by an energy system that includes a capacitor connected in parallel with a smaller battery. Here, the capacitor effectively lowers an impedance of the energy system. During a current pulse, a properly selected capacitor will reduce a voltage drop in the system because of its lower equivalent series resistance (ESR). To keep size and weight to a minimum, the capacitor may be chosen to have a maximum operating voltage not substantially greater than an operating voltage of the device.
In addition to having a main energy source interface for connecting with a main energy source, a device may include an auxiliary energy source interface to connect with an auxiliary energy source. An auxiliary energy source may be a larger energy source, such as an automobile battery, that does not present the problems associated with smaller batteries. Thus, an operator of the device has an option to prolong the operating time of the device by using the auxiliary energy source. An auxiliary energy source may provide a nominal operating voltage that is larger than that of the main energy source.
Accordingly, what is needed is an electronic circuit that accommodates and further supports these and similar needs of portable electronic devices, and especially one that is suitable for low voltage applications with large current pulse requirements.